Back in the early 90s, the Lemmings game worked. So how come after purchasing a second copy of this disk + downloading the adf does Lemmings still not work on my A500. It goes to a green screen and sits there.

When is the green screen appearing?. On reboot or after the execution of the game?.
I'm asking because green screen are chip ram problems. Hope this is not the case.

Well, I press F3 for the lems demo. Goes to workbench prompt, then back to the menu, the I get that stripey fx splash thing. Then to a green screen, the time it works, the green screen is usually on for about 10 seconds - with the disk drive clucking like a chicken.
I only have 512k ... even though I've got this 2MB ram upgrade (the one from amigakit) but I only just found out it's FS(2 more letters here can't remember the name i'm so bad on the techy side ) instead of PAL ram. It's still in there now so I guess I've still only got 512k of ram.

That's is. I'm so embarrased, I even want to try and learn this tech stuff too!

anyway, Apart from ram it could be something odd about this disk anyway. In another thread, some one mentioned it had like 81 floppy bocks instead of the usual 79 blocks. This could be cheated on easyADF by just adjesting the block box. but no one knew why it was the only coverdisk with 81 blocks.